Trump has contradicted himself on a regular basis and said many misleading statements since taking office and during the presidential campaign. His frequent falsehoods have prompted a debate by observers about whether to call them "lies," a label critics say suggests an intent that may not always be clear.

Yet his rise to political stardom was built on his spreading the false "birther" theory that President Barack Obama was born in Kenya and not a US citizen. Beginning in 2011, Trump led the charge calling for Obama to release his long-form birth certificate, which he eventually did. Trump did not publicly reverse his comments until last September during the election, five years after he initially pushed the conspiracy theory.

"President Barack Obama was born in the United States," he said. "Period."

He then blamed the 2016 Democratic presidential nominee, Hillary Clinton, for starting the falsehood, saying: "Hillary Clinton and her campaign of 2008 started the birther controversy. I finished it. I finished it — you know what I mean." That claim has never been substantiated.

Trump's tendency to spout falsehoods also led the former FBI director James Comey to testify under oath that he did not trust the president to be honest about the nature of their private meetings.

When asked by the Senate Intelligence Committee chairman, Richard Burr, why he documented his interactions with Trump more meticulously than he did with Obama while serving as FBI director, Comey replied: "I was honestly concerned that he might lie about the nature of our meeting, and so I thought it really important to document."